how common are mutations during dna replication? a. about 5 nucleotides in 6.5 billion are changed during each replication. b. about 50 nucleotides in 6.5 billion are changed during each replication. c. no nucleotides are changed during each replication. d. about 5,000 nucleotides in 6.5 billion are changed during each replication. e. about 500 nucleotides in 6.5 billion are changed during each replication.